Feedbooks has a list of some fifty free military and historical books.
Publisher TOR is offering a free ebook copy of Martha Wells’ All Systems Red science fiction mystery.
Rudi Geudens has a site that has images and descriptions of classic wargaming books. I’ve got some of those — or had some of those — and its a neat trip down memory lane.
All 6,000 plus pages of the classic fantasy comic Elf Quest now are online.
Philip Haythornthwaite’s The Napoleonic Sourcebook is a good place to start for a basic understanding of the Napoleonic Wars. The volume is divided into six major sections: The Campaigns, Weapons and the Practice of War, The Nations Involved in the Wars, Biographies, Sources, Miscellaea and a useful glossary. There are more than 200 black and white illustrations, maps and charts. For the painter, the book has descriptions of various uniforms and lists of uniform, facing, hat and button colors.